Process control of flotation beneficiation of composite ores often is based on the relative concentrations of particulate translucent and opaque components in the ore. Typically, these concentrations are visually estimated by plant operators. It is widely recognized that because such estimates are subjective, they therefore vary from operator to operator. Also, such subjective estimates are imprecise and inaccurate.
Various methods and apparatus for the image analysis of particles are known. For example, U.S. Pat. No. 4,136,950 discloses a microscope system for observation of small particles in motion, such as particles emanating from an aerosol container. A video camera is used to observe the particles through stop action photography by the use of strobe lighting to create an image. The image then is stored in a short-term memory. The stored image is converted to electrical image-information signals by scanning the camera's imaging device, in accordance with the conventional operation of such a camera. The patent further discloses use of a `shading corrector` positioned in front of the camera to correct differences in background brightness and ensure that the background appears uniformly bright.
U.S. Pat. No. 4,617,682 discloses an apparatus and method for automatic quantitative measurement by image analysis of textures of optically anisotropic material having a known anisotropic nature. In particular, the patent is directed to quantitative analysis of coke. In accordance with the method of this patent, extensive sample preparation is required. The anisotropic material, for example, coke particles, is imbedded in resin visually distinct from the material. The reflectance pattern of the coke-containing resin is viewed through a polarizing microscope. The pattern is stored as grayscale information from an image divided into pixels; the resin has a grayscale value lower than that of the coke. Differences between grayscales of a base set of pixels and grayscales of subsets of pixels surrounding the base set of pixels are determined. The reflectance patterns are determined from these differences by comparison to pre-determined differences corresponding to the various textures (i.e., anisotropic areas) of the coke. Grayscales lower than those of the coke, which indicate that the primary component detected by the pixel is resin, are eliminated from consideration by pre-established criteria. Use of this method is burdensome, and requires mounting of the particles in resin.
U.S. Pat. No. 4,561,018 discloses an apparatus for viewing particulate matter, especially snow and other solid hydrometers. Particles are moved into the field of view of the camera, where motion of the image can be stopped by a strobe lamp.
U.S. Pat. No. 4,814,868 discloses an apparatus and a method for identifying moving particles by filtering image information to eliminate not only `noise` but also stationary objects and variations in the background.
The subject invention provides an apparatus and method for the image analysis of composite ores, whereby the relative concentrations of translucent and opaque components are reliably, accurately, and quickly determined. More specifically, the subject invention provides an apparatus and method for the image analysis of phosphate ore, whereby the relative concentrations of phosphate and quartz are determined.